The present invention relates to a color management method and apparatus for a printing press, which are suitable for color matching between a color proofing print and printing products printed by a printing press.
Generally, when printing products are ordered, a color proofing print is presented to the customer in advance to confirm the tint of final printing products. More specifically, a color proofing print is output using a color proofing apparatus (flat-bed proofing machine, color printer, DDCP (Direct Digital Color Proofer), or simplified proofing machine) and presented to the customer to confirm whether the tint is appropriate. If the customer agrees to the tint, the ink supply amount of each color in a printing press is adjusted so that actual printing products have the same tint as that of the color proofing print.
However, it is very difficult to print the same tint as that of the color proofing print by adjusting the ink supply amount of each color in the printing press because the color proofing apparatus and printing press have different color reproduction characteristics, resulting in troubles between the customer and the printing company.
Recently, the color reproduction characteristics of the color proofing apparatus and printing press are checked in advance, and color proofing is done by tint according to the tint of printing products printed by the printing press, thereby preventing troubles with the customer. More specifically, a profile representing the color reproduction characteristic of the color proofing apparatus is compared with a profile representing the color reproduction characteristic of the printing press, and the dot area percent of each of a plurality of standard ink colors in outputting a color proofing print, i.e., the ratio (%) (printed area of a color per unit area) of dots of each of four standard ink colors (to be referred to as ink colors hereinafter), including three primary colors of process inks: yellow, magenta (red), and cyan (blue), and India ink (black) is adjusted such that the color proofing print and printing products printed by the printing press have the same tint. This processing of adjusting the tint to obtain the same colors by the apparatus and printing press is called color matching.
The profiles of an existing color proofing apparatus and printing press provided by press makers have large error because a printing company employs various output conditions and printing conditions (e.g., output and printing environments, printing materials, inks, paper, reference densities, and client requirements). For this reason, the profiles of color proofing apparatus and printing press are individually generated using a manual measurement device under the output and printing conditions in the printing company.
Conventionally, however, since color data of printing products is measured by a manual measurement device in generating the profiles of a color proofing apparatus and printing press, measurement takes a time. Especially, the profiles of the color proofing apparatus and printing press change depending on their outputs and printing environment (ambient temperature and humidity) and therefore must be periodically measured. However, since measurement is time-consuming and cannot be done at a short interval, color matching is executed while keeping large error remaining, resulting in poor precision.
Additionally, manual measurement must wait until inks dry to prevent damage to the printing products. As inks dry, the printing products lose gloss and have subdued colors. When color data is sampled from the printing products having subdued colors, a difference is generated between the color data and that immediately after printing, resulting in poor color matching precision.
Furthermore, conventionally, the measurement device used to generate the profile of the color proofing apparatus is different from that used to generate the profile of the printing press. Accurate color matching is impossible because of the difference in characteristics between the measurement devices.